Orion Wagner, 6 and-a-half, watches as a train rotates in the roundhouse on the train layout at the Randall Museum on May 7, 2014 in San Francisco, Calif. The Golden Gate Model Railroaders may have to dismantle their train layout before the end of the year to accommodate a renovation by the Randall Museum, where the layout is housed. less

Orion Wagner, 6 and-a-half, watches as a train rotates in the roundhouse on the train layout at the Randall Museum on May 7, 2014 in San Francisco, Calif. The Golden Gate Model Railroaders may have to dismantle ... more

A train passes through a mountainous section of the train layout at the Randall Museum on May 7, 2014 in San Francisco, Calif. The Golden Gate Model Railroaders may have to dismantle their train layout before the end of the year to accommodate a renovation by the Randall Museum, where the layout is housed. less

A train passes through a mountainous section of the train layout at the Randall Museum on May 7, 2014 in San Francisco, Calif. The Golden Gate Model Railroaders may have to dismantle their train layout before ... more

A train passes through a mountainous section of the train layout at the Randall Museum on May 7, 2014 in San Francisco, Calif. The Golden Gate Model Railroaders may have to dismantle their train layout before the end of the year to accommodate a renovation by the Randall Museum, where the layout is housed. less

A train passes through a mountainous section of the train layout at the Randall Museum on May 7, 2014 in San Francisco, Calif. The Golden Gate Model Railroaders may have to dismantle their train layout before ... more

It's the very model of a world in miniature. More than 600 feet of track run through the smallest of small towns, in and out of faux mountains by way of carefully crafted tunnels and bridges. The club owns more than 300 rail cars, including complete old streamliners and modern Amtrak train sets. There are freight cars of every description and at least 30 locomotives.

Freight trains pulled by steam engines chuff through the mountains and roar through the towns, their whistles blowing for the highway crossings, two long blasts, a short and a last long, lingering whistle, just as they did in the world of your grandparents.

"It's monumental. It's colossal. It's priceless." said Robert Herman, a San Francisco architect who discovered the model railroad when he brought his granddaughter to visit the Randall Museum the other day.

Herman has a soft spot in his heart for model railroads. When he was a kid in Newton, Mass., he built trains and ran them on rainy afternoons. The experience taught him about miniaturization and attention to detail.

"I really think becoming an architect had a lot to do with those rainy afternoons with model trains," he said.

But in talking to the model railroaders, he learned there is big trouble ahead for the little railroad.

The city has received a $5.6 million grant to renovate the museum. Among other things, the money would be spent to bring the 63-year-old structure up to the city building code and meet Americans with Disabilities Act standards.

So down here in the basement is this funky railroad layout, built more than 50 years ago of chicken wire, papier mache, miniature rails and devotion. Some of the city's proposals would reduce the size of the railroad, or remove it entirely.

In the worst case, said Jim Willcox, the model club's secretary-treasurer, "The layout as you see it would have to go into the trash bin."

The best case, he says, is that the layout would stay the same, with minor modifications to improve public access.

The city says the building has to meet building codes and accessibility requirements. "We want them there," said Sarah Ballard, of the city's Recreation and Park Department. But, she says, there have to be some changes. For one thing, the railroad, which she calls "an exhibit," has to be open longer hours - ideally 10 a.m. to 5 p.m. five days a week. For another, there would be a new floor plan with "ample space" for the railroad.

So the two sides sit, like a train stuck in the station, stalled while something is blocking the tracks down the line.

When he's not worrying about the railroad's future, Willcox, a retired lawyer, operates the trains. His pride and joy is a model Union Pacific "Big Boy" steam locomotive, in real life one of the largest ever built. His engine is a foot and a half long, a model monster in a world where 0.1378 of an inch equals 1 foot in the real world.

The engine has 16 drive wheels, and has a sound control in the tender so that it huffs and puffs like the real thing. Willcox has been interested in model trains most of his life, and once, in Nevada, a couple of years ago, he operated a full-size locomotive.

"It gives you a feeling of power. You pull back on the throttle slowly and it moves," he said. "A steam locomotive is like a living, breathing thing."

Nick Wright has never driven the real thing; he sticks to models. It runs in the family.

"I got my first train set when I was 3 hours old," he says, "so it has always fascinated me."

He's 18 now, a senior at Capuchino High School in San Bruno. He's going to San Jose State in the fall, majoring in mechanical engineering.

Biggest little railroad

The Golden Gate Model Railroad Club will be open Saturday for the semimonthly Junior Engineer Day. From 10 a.m. to 3 p.m. children can take turns running the model trains. More information at http://ggmrc.org.

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